Effect of lower voltages on amp

[gayler]

What would be the effect on power output and tone if the voltages at the filter caps are lower than normal. The reason I ask is because I would like to build an 18watter from an old console amp. When I messure at the can cap with all tubes in place and the amp playing I get 223 volts with a line voltage of 120vac. Mark huss' 18 watt minimalist shows 305V at the first cap. Will it work with the lower voltage? If so how will it effect the amp?

[olddawg]

Originally Posted by gayler

What would be the effect on power output and tone if the voltages at the filter caps are lower than normal. The reason I ask is because I would like to build an 18watter from an old console amp. When I messure at the can cap with all tubes in place and the amp playing I get 223 volts with a line voltage of 120vac. Mark huss' 18 watt minimalist shows 305V at the first cap. Will it work with the lower voltage? If so how will it effect the amp?

Is it a tube or an SS rectifier? If it is a tube and you convert it to a full wave SS bridge you will increase the B+. That said a lower B+ will reduce the output power and have an effect tonally. You may or may not like it. Did the amp originally have EL84s in PP?

[gayler]

It has a SS rect. It has two el84 stereo single ended, one for each channel. Just wonder what it would sound like with lower voltage? Also would it be better to keep it single ended, or go push pull with the correct output transformer?

[olddawg]

Originally Posted by gayler

It has a SS rect. It has two el84 stereo single ended, one for each channel. Just wonder what it would sound like with lower voltage? Also would it be better to keep it single ended, or go push pull with the correct output transformer?

Since it is stereo with a lower voltage PT, I would probably pass on it altogether. It woundn't be expensive or time consuming to set it up as a single ended guitar amp though. It just won't be as loud and gutsy as it would with a higher B+. If you spend the money and time for a full PP conversion with a new OT, you are likely to be disappointed if you are expecting a screaming 18 watt Marshall clone variant. I would sell it on eBay and look for something else or use the money to buy a good Heyboer transformer set. I've done some conversions. I find it better to be picky about the iron and build up from a new chassis, ceramic sockets, and new components. Its great if you can get the right iron and vintage tubes. Anything else tends to be problematic IMHO.

[gayler]

i wondered if the fact that it had all the tubes for the radio in it if that wass drawing down the voltage some? being as im doing this on a nea rzero budget mostly for fun i thought i could get a cheap pp output transformer and maybe make it work. sorry for the bad typing, im feeding my three monyh old son.

[olddawg]

Originally Posted by gayler

i wondered if the fact that it had all the tubes for the radio in it if that wass drawing down the voltage some? being as im doing this on a nea rzero budget mostly for fun i thought i could get a cheap pp output transformer and maybe make it work.

Yeah you could do that. Keep in mind that the radio was designed for clean gain. If the PT has a lot of excess current capacity you could try a voltage doubler B+ and 6V6 finals. I would do this only if you can find a 6v6 doner amp with a blown PT though.